No, I still here but trying to learn the fabrication requirements for a Class 1 Div 2 PLC enclosure; mainly because I think our vendor misrepresented the classification of his design. By the way the PLC control panels and junction boxes are non-purged enclosures with Allen Bradley Compact Logic PLC components which are rated for Class 1 Div 2; but there are no IS Barriers. Also you are correct the terminal blocks are not rated for Class 1 Div2 areas as far as I can see. I think we have a problem but maybe I am wrong, please advise and documentation links would be greatly appreciated. Thanks
For this kind of thing you are looking at non-incendive protection from explosion. You would not need intrinsically safe barriers or purging.
For the most part the only thing you have to worry about are things that might get hot or spark such as a hard contact. Terminal blocks are not an issue.
You might want to read carefully the sections of the code that refers to this protection technique. Unfortunately it's not like it's all in one spot. It is kind of scattered through articles 500 and 501. And you have to read pretty carefully what it actually says rather than what you think it says. It's also somewhat confusing because equipment that is non-incendive is generally not labeled that way. It just says it is okay for class one div two for instance. For some reason the UL product standard does not require it to be labeled as NI.
There is a good chance that you could make a PLC control panel that would be perfectly acceptable for a division 2 area without any special protection means other than NI. I have to admit I am a little nervous about your use of the term access holes to describe how the field wires come into the control enclosure.
If there are motor starters or relays in the box, it probably can't be non-incendive.
